avcodec/diracdec: Check bytes count in else branch in decode_lowdelay() too

Fixes: signed integer overflow: 8 * 340018243 cannot be represented in type 'int'
Fixes: 9441/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-5194665207791616

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/diracdec.c

@@ -986,6 +986,10 @@ static int decode_lowdelay(DiracContext *s)
             for (slice_x = 0; bufsize > 0 && slice_x < s->num_x; slice_x++) {
                 bytes = (slice_num+1) * (int64_t)s->lowdelay.bytes.num / s->lowdelay.bytes.den
                        - slice_num    * (int64_t)s->lowdelay.bytes.num / s->lowdelay.bytes.den;
+                if (bytes >= INT_MAX || bytes*8 > bufsize) {
+                    av_log(s->avctx, AV_LOG_ERROR, "too many bytes\n");
+                    return AVERROR_INVALIDDATA;
+                }
                 slices[slice_num].bytes   = bytes;
                 slices[slice_num].slice_x = slice_x;
                 slices[slice_num].slice_y = slice_y;